I develop a web application and we test it on browsers like Firefox and Internet Explorer. During our development we test the application on Firefox 3.5.2 and our testing team tests the same on 3.5.6 and found the UI looks good. But all of the sudden the client complains that it doesn't look good in 3.5.8.

How do we handle these minor version issues? How can we check the browser compatibility during development and during testing?

Is there any tool to test the application on 3.5.X, X being all the minor versions?

This is exactly why I stopped making web applications. The only advice I could give you is try to isolate the browser-specific stuff in such a way that you never have to edit your "good code". This can be quite hard, as each browser behaves different at so many different points...
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deltremeSep 27 '10 at 11:57

There are several tools that let you check major and some minor versions of websites by comparing screenshots and unit testing frameworks that let you automatically drive the browser and both content AND functionality are correct. If time is an issue, I would suggest option #1. If you have time to write unit tests, which is the better option, then go with option #2.

Try http://browsershots.org/. There are others as well that do the same thing. Without much work at all you can do spot checking of hundreds of browsers and versions.

If you want to get more detailed, I would suggest writing web UI unit tests that give you more control over your testing. Great libraries include Selenium (C#, Java, Ruby and many more), or WatiN.

Writing Selenium code in a JUnit unit test is not unit testing. It's integration/system testing being run by a unit testing platform. Unit testing means you test a single unit of code in isolation, for example a single method on a single object. Browser testing is NOT unit testing.
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Jaco PretoriusSep 27 '10 at 18:42

This is one solitary confined case where I would say IE has the edge over other browsers.

Version released. BAM! Nothing till the next version. It has issues? Work around them. The key here is the issues are consistent and repeatable bugs. Firefox has about a half dozen versions in active use, from 3, 3.5, 3.6, 4, and the ones in between. Does everyone keep up on their version? Probably not.

I recommend testing in the latest stable build of Firefox, Chrome, Safari, and of course IE 7/8. If someone mentions an issue specific to another browser, open it up and make a fix. This could involve a compromise in design or reduction in the stylization level on the page.